What is end game?
The short version of end game is that your character has reached maximum level. Which at the time of this writing is 80. This max level has fluctuated overtime with the level cap being dropped at least once to streamline the process and combat stat inflation. There are many end game activities but the three main ones as outlined in the intro page are mythic dungeons, raids, and collectables.
Mythic Duengons
This End Game is the process of running harder and harder dungeons. After completing your first M0. You will be given a Key that is for a specific dungeon and once used starts a timer. If you beat the timer you get a key for a new mythic that is higher level. Titles, Achievements, Cool Armor, and bragging rights await those that push keys to the highest levels. See video below for more information.Raids
Raid come in 4 difficulty levels. Looking for Raid, which works the same way as the random dungeon finder and you can queue for it. Normal, Heroic, and Mythic. Each difficulty level gives better gear however mechanics, damage, and health are added to each boss. See video below for more information.Collectables
This is end game for pretty much everyone in the game in some form or the other. Collectables include mounts, battle pets, armor/weapon appearances, achievements, artifacts, toys, and more. many of these can be difficult, time consuming, pure luck, or some combination of the above to get. Each expansion adds more to this list. See video below for more information.
Thanks for reading!